Cell Shape

How is the shape of the cell determined? Little is understood how nano-sized components can assemble into defined structures microns in size. Fission yeast, along with bacteria such as E. coli, serve as simple models for developing concepts in cell morphogenesis (Chang and Huang, 2014). These cells are single-celled rods whose shape is dictated by their cell wall. The cell wall is a 200nm thick mesh composed primarily of beta glucan fibers. Our measurements show that fission yeast cells have high turgor pressure (1.5 MPa, or 15 atm, roughly the pressure inside a racing bike tire), contained by an elastic cell wall (with an elastic modulus roughly similar to tough tire rubber)(Minc et al., 2009Atilgan et al., 2015).

Knowing that the cell is under such high internal pressure changes our perspective of various cellular processes. The turgor pressure for instance is highly relevant to mechanisms of cytokinesis and endocytosis, as it opposes ingression of the plasma membrane (Proctor et al., 2012Basu et al., 2014). Physical mechanisms play a large role in determining cell shape. The cell wall is inflated by turgor pressure. Just after cell division, turgor pressure may inflate the septum cell wall to form the rounded shape of the new end (Atilgan et al., 2015). 

Ongoing projects are investigating additional aspects of cellular morphogenesis from a physical perspective, trying to integrate biomechanics with cell polarity and cell wall assembly mechanisms.